This variable, which defaults to null, can be used to track the number of buildings that have actually been built. This number has no impact on the model.

Dropdown menu items for setting or clearing the builtBuildings value have been added for each recipe row.

These items mirror the behavior and implementation of those for fixedBuildings, for the most part.
The initial value is buildingCount rounded up, or 0 if buildingCount is negative.
As 0 is a valid value, clearing builtBuildings returns it to null.

Shopping lists now use the builtBuildings value instead of buildingCount if the former is not null.

The text field is only visible if builtBuildings is not null, and is placed under the building count. It is colored grey to indicate that it is not playing a role in the model.

If the number of buildings needed for the model's solution is greater than the specified number of built buildings, the recipe will now be flagged accordingly.
This makes it substantially easier to determine which recipes need to be revisited if a change is made.

To make issues more apparent, the entire page now displays an error message (like with deadlocks) if a recipe needs more machines than it currenty has built.